1. Field of the Invention
The invention relates to a vehicle and a contactless power supply system and, more particularly, to a technique for improving power transfer efficiency in a contactless power supply system.
2. Description of Related Art
In recent years, contactless wireless power transfer that does not use a power cord or a power transmission cable has become a focus of attention, and it has been suggested that the contactless wireless power transfer is applied to an electric vehicle, a hybrid vehicle, or the like, of which an in-vehicle electrical storage device is chargeable by a power supply outside the vehicle, (hereinafter, also referred to as “external power supply”).
In such a contactless power supply system, in order to improve power transfer efficiency, it is important to match impedance between a power transmitting side and a power receiving side.
Japanese Patent Application Publication No. 2012-034494 (JP 2012-034494 A) describes a configuration that an impedance matching unit provided between a power generating unit and an electric power supply point in a power supply device and an impedance matching unit provided between a power receiving element and a load in a power receiving device are provided in a system that is able to contactlessly supply electric power.
In a contactless power supply system that contactlessly transmits electric power from a power transmitting device to a vehicle, power transfer efficiency can vary depending on a distance between a power transmitting unit in the power transmitting device and a power receiving unit in the vehicle. This variation in distance includes a vehicle height that is a vertical distance between the power transmitting unit and the power receiving unit and a positional deviation that is a horizontal distance between the power transmitting unit and the power receiving unit.
For example, if an occupant gets on to the vehicle or gets off from the vehicle or a baggage is loaded into a trunk room or unloaded from the trunk room while power transmitting operation is being carried out from the power transmitting device to the power receiving device (vehicle), the vehicle height varies accordingly, so the input impedance of the power transmitting unit may fluctuate and the power transfer efficiency may decrease.